Hello @eternalNewbie.
To inline the xml into the client side code like you are doing you should use rc/inline
like this:
(ns demo.app
(:require [shadow.resource :as rc]
["xml2js" :as xml2js]))
(def domaines-xml (xml2js/Parser (rc/inline "data/domaines.xml")))
Note that you should put the file on the classpath e.g. in src/data/domaines.xml
if you use this method.
See this post for more details.
If you want to use express.js on your backend might I recommend Sitefox which is a ClojureScript backend framework I built specifically for this. It is built on top of express. You can bootstrap a new project like this:
npm init sitefox-shadow-fullstack myproject
Let me know if I can help in any way.